Cause analysis of surface cracks in flash butt welding joint of high manganese steel frog

Abstract

Surface cracking is one of the typical failures in butt welding joints of high manganese steel railway frogs. Understanding the formation mechanism of such cracks can effectively prevent similar failures from occurring. Herein, assisted with multiple macro and micro characterization tools, we discussed the causes of surface crack formation for a flash butt welding joint of a high manganese steel frog. The results show that the surface cracks are typical intergranular stress corrosion cracks (IGSCC) distributed near the fusion line between the carbon steel rail and the stainless steel medium in the stainless steel side. Acicular martensite exists near the fusion line between carbon steel rail and stainless steel medium, and the residual stress is large. At the same time, there are continuous network chromium carbide precipitates on the austenitic grain boundary of stainless steel. The above two points should be the main reasons for the initiation of cracks on the weld surface. Reduce the proportion of martensite structure by reasonably optimizing the welding cooling rate. Properly temper martensite to reduce the hardness and internal stress in the transition zone. These measures can prevent the occurrence of intergranular cracks on the weld surface.